There are several to answer DS questions (I am sure I'll forgot lots of them but let me try
- if the question is speaking about x, y, z and you have
(1) something about x
(2) something about z and y
The answer cannot usually be A, B or D. So in a sec you can see where to look at.
However, be careful of the question is x^2 * y * z^3 > 0. It is also obvious in that case that x is not needed ! So here, it can't be A, and it can be B or E, only !
- you have two unknowns, and no equation given!
(1) one equation with x and y
(2) another equation with x and y
In that case, it can't be A, B or D. First thing to do, check if (1) and (2) are equivalent! If they are, the answer is, all simply, E. If they are not, don't even think about checking the result, it's C, for sure! 2 equations (not equivalent), 2 unknows ==> answer for sure! I never saw a question like that with two contradictory equations (like a+b = 5, a+b = 2).
I think that with those points you can easily get through the 500 questions!
- you can have a question with a really tough equation!! something like
is (x-1)^2 - 1 > (x-2) ??? Think SIMPLIFICATION!!!!!
==> (x-1)^2 - 1 = x*(x-2) (two ways : A^2-B^2 = (A-B)(A+B) or just develop!)
so now we have is x(x-2) > (x-2) <=> x > 1 for x =! 2 (=! : different)
Now just have a look at the statements and I am sure you can answer the question very fast!
- You have the questions with a lot of talking! Put aside what is uneeded and write down all the elements that are given to you to answer the question. Then write down an equation and even before having a look at the statements, ask yoursel=> what do I need to solve this "flipping" problem?
The answer will come to you afterwords.
- Now you have the most complicated one. The one that implictly ask you to find counterexample! Indeed, every time you feel uncomfortable with a question (like those with the sets :') ), try find a counterexample!! At first it will seem to you to be veeeeerrryyyy tough but once you will have done lots and lots of question like that, the counterexmples will be quite easy to find (note that I said "quite"...
Finally, when you have questions with, x, y, z, always ask you the following : HOW ABOUT ZERO ???????
Hope it helps
Oh, and I am sure that I forgot a looooot (I don't have time, I am at work) and that I made a lot of mistakes(I am not english native speaker) so feel free to correct me or add some ideas